// 13001. 反转链表 - 迭代
Node *solve(Node *head)
{
    Node *newHead = NULL; // 指向新链表头节点
    Node *p;              // 指向挪动节点
    while (head != NULL)
    {
        p = head;
        head = head->next;
        p->next = newHead;
        newHead = p;
    }
    return newHead;
}